Mass flow rate

Mass flow rate is the mass of substance which passes through a given surface per unit time. Its unit is mass divided by time, so kilogram per second in SI units, and slug per second or pound per second in US customary units. It is usually represented by the symbol $\dot m$.

Mass flow rate can be calculated from the density of the substance, the cross sectional area through which the substance is flowing, and its velocity relative to the area of interest.

$\dot m = \rho \, v \, A$

where:

${\dot m}$ is the mass flow rate

ρ is the density

v is the velocity

A is the flow area

This is equivalent to multiplying the volumetric flow rate by the density.

${\dot m} = {\rho \cdot Q}$

where:

ρ is the density

Q is the volumetric flow rate

The symbol for mass flow rate in Newton's notation for a derivative is as follows:

$\dot m = \frac{dm}{dt}$

See also

• Continuity equation
• Fluid dynamics
• Mass flow controller
• Mass flow meter
• Mass flux
• Orifice plate
• Thermal mass flow meter
• Volumetric flow rate